v1.1.0

• The dichromat() function now offers a pass-through (normal colour vision) option, and is also vectorised over its second argument (#3). Some of the coefficients it uses internally are now pre-calculated and cached for efficiency.
• There is now a print method for vectors of class shade.
• An empty shade vector is now explicitly an error.
• The README now includes an example of using shades with ggplot2 (#2), as well as links to several related packages.